Power bank



FIG. 1 is a perspective view of a power bank showing our new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top view thereof;

FIG. 7 is a bottom view thereof; and,

FIG. 8 is a perspective view viewed from another visual angle thereof.

CLAIM The ornamental design for a “power bank,” as shown and described. 